Sample Donor Acknowledgement Letter for Cash Donation. This booklet contains: Form 100S, California S Corporation.You can claim back the difference between the tax you've paid on the donation and what the charity got back when you fill in your Self Assessment tax return. Attach copies of your pay stubs for the last two months and proof of any other income. Include the nonprofit's EIN so the the donor can to check the charity's tax-exempt status with the IRS. What do you need to include in your donation acknowledgment letter? We make it easy to donate online, with a safe, secure online donation. You can make a one-time or recurring donation. Please keep this written acknowledgement of your donation for your tax records. Further financial or program information to help me make a decision about giving.